gaasu

Gaasu, written in Japanese as ガス, is the term used for gas in general. In English-language discussions about Japanese sources, gaasu may appear as a romanization, but the standard transliteration is gasu. In everyday Japanese, gaasu refers to any gaseous substance used for energy or industrial purposes, as well as to the gaseous state of matter itself. The word is widely used for household and commercial applications, such as natural gas for cooking and heating (天然ガス) and bottled gases for various industries (ガス缶, ガス器具).

In science, gas is one of the four fundamental states of matter, characterized by indefinite shape and volume, low density, and the ability to be compressed and to flow. Gases expand to fill their containers and mix thoroughly with other gases. The behavior of many gases can be described by the ideal gas law PV = nRT, which connects pressure, volume, temperature, and amount of substance. Real gases show deviations at high pressures or low temperatures, but the model provides a useful approximation for many practical purposes. Gas properties arise from molecular motion and interactions, as described by kinetic theory.

Common gases include nitrogen, oxygen, carbon dioxide, hydrogen, methane, and the noble gases. In industry, gases are produced, stored, and transported in specialized forms: natural gas (predominantly methane) for energy, liquefied petroleum gas and bottled gases for cooking and heating, and industrial gases such as helium, argon, and nitrogen used in manufacturing and research. Safety is important: many gases are flammable, toxic, or asphyxiating, requiring proper ventilation, leak detection, and handling procedures.

Historically, the term gas originated in early modern science and entered Japanese with Western scientific import in the late 19th century, aligning gaasu with the global concept of gaseous matter and its applications.